EVOH resin can exhibit superior excellent gas-barrier performance such as oxygen-barrier performance due to the fact that hydrogen bond is formed between hydroxyl groups in the molecular chain of the EVOH resin to form a crystal which can prevent oxygen from intruding. For this gas barrier performance, EVOH resin is shaped into a film or sheet used as a wrapping material for food, pharmaceuticals, industrial medicine and agrochemicals, or container such as bottle.
In general, shaping EVOH resin into film, sheet, bottle, cup, tube, or pipe is performed by melt-molding. The resulting molded article is processed for actual use. Therefore moldability and processability are important properties for EVOH resin.
A patent document 1 discloses that melt-molding a composition having an increased melt viscosity is advantageous among compositions comprising a boric acid or a salt thereof in film formability of melt-moldable vinyl alcohol-based copolymer such as EVOH resin-based copolymer, in particular, prevention of surging in film forming process.
A patent document 2 discloses that EVOH resin treated with use of a boron compound is extruded with polyolefin to provide a layered film exhibiting an excellent adhesiveness between the EVOH resin layer and the polyolefin layer. The layered film can provide a wrapping material preferably usable in the field that gas barrier performance is required.
According to the patent document 2, the treatment with use of a boron compound may be conducted by adding the boron compound to EVOH resin solution or dispersion. The obtained EVOH resin pellet contains the boron compound and uses as a raw material for extrusion molding.
Recently the appearance of a wrapping material becomes important, therefore EVOH resin film or multilayer structure needs to be reduced in minute fish eye having a size less than 0.1 mm.
A patent document 3 discloses that a boron-containing EVOH resin pellet obtained by a process of permitting a boron compound to be contained in an EVOH resin pellet has a relation between the water amount contained in the pellet and the occurrence of minute fish eye having a size less than 0.1 mm. Also the patent document 3 discloses that the number of minute fish eyes can be dried until the water amount is reduced to 0.0001 to 2% based on the weight of the pellet and contacting the pellet with water.
According to examples of the patent document 3, a 3-type 5-layer film was produced with use of EVOH resin pellet in which the content of water and the content of boron were adjusted. The EVOH resin pellet contains water in an amount of 0.13 to 0.4%, and boron in an amount of 0.015 to 0.039 parts relative to 100 parts of EVOH resin, i.e. 150 to 390 ppm. Such EVOH resin pellet was produced by immersing in water the EVOH resin pellet containing a boron compound and drying it. Thus obtained EVOH resin pellet was fed to a multilayer type extruder to produce a 3-type 5-layer film as shown in Examples 1, 3, and 4. Evaluation of the occurrence of fish eye in the multilayered film was conducted by visually observing and counting minute fish eye having a diameter of 0.01 to 0.1 mm (see paragraphs 0038-0041).    Patent document 1: JP 562-3866B    Patent document 2: JP H3-11270B    Patent document 3: JP2000-44756A